Genetic Code & mRNA translation Flashcards
What does thymine pair with in RNA?
uracil
Describe the characteristics of the genetic code
non-overlapping, universal, degenerate, triplet code
Why is the genetic code degenerate?
a single amino acid is made by more than one codon
What is the advantage of the code being degenerate?
Tolerance to mutations
What are the most frequently occurring amino acids?
arginine, leucine and serine
What are the stop codons?
UAA, UAG and UGA
What is the function of transfer RNA?
incorporate correct amino acid residues
Describe the characteristics of tRNA
adaptor, bifunctional, specific to one amino acid
What corresponds to each codon on mRNA?
anti-codon on tRNA
Describe wobble base pairing
pairing between two nucleotides in RNA molecules that does not follow Watson-Crick base pair rules
Why does wobble base pairing occur?
one tRNA can recognise more than 1 codon
Describe the characteristics of the ribosome
mRNA decoder, protein factory, small and large subunits,
rRNA,
What are the three sites in ribosomes?
A, P and E
What does the E site stand for in ribosomes?
Exit
What subunit catalyses the peptide bond? (ribosomes)
large 60s subunit
What is the function of the small ribosomal subunit?
codon matching
What is the effect of antibiotics on ribosomes?
bind to pockets formed by rRNAs and block translation
Where do the pockets antibiotics bind to exist (ribosomes)?
ONLY in bacterial ribosomes
Describe the effect of tetracycline
blocks binding of aminoacyl-tRNA to A site of ribosome
What is the first step of protein translation?
tRNA binds to codon by complementary base pairing
What is the second step of protein translation?
Peptide bond formation between residue 3 and 4
What is the third step of protein translation
large subunit translation - A site opens
what is the fourth step of protein translation?
Small subunit translation
Describe how the ribosome moves along mRNA in the fourth step of translocation
from 5’ prime to 3’ prime end, one codon at a time, until it reaches a stop codon
How is the peptide bond formed?
condensation reaction catalysed by peptide transferase
What is the effect of stop codons on the ribosome
bind a release factor into A site of ribosome, causing disassembly of ribosome
What does RNA polymerase allow
Simultaneous transcription of genes